RFR: Update the readme to include IntelliJ setup instructions [v2]

[Robin Westberg]

> Adds a section on how to build and test Skara using IntelliJ IDEA.

Robin Westberg has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Update readme to include IntelliJ setup

-------------

Changes:
  - all: https://git.openjdk.java.net/skara/pull/998/files
  - new: https://git.openjdk.java.net/skara/pull/998/files/16591a58..58f33fd7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=998&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=998&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/998.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/998/head:pull/998

PR: https://git.openjdk.java.net/skara/pull/998